PROJECT DESCRIPTION: This R01 project's goal is to investigate the mechanism by which cold-inducible RNA-binding protein (CIRP) increases sepsis severity and causes acute lung injury (ALI). Sepsis and ALI are deadly and have no FDA-approved treatment. CIRP is a nuclear protein that can be released into the circulation during sepsis, increasing sepsis severity and causing ALI. We have discovered that CIRP increases a novel subset of neutrophils characterized by surface expression of intercellular adhesion molecule- 1 (ICAM-1). We found that ICAM-1+ neutrophils were expanded in the blood and lungs of septic mice, but not in CIRP knockout mice. We further showed that stimulation with CIRP was sufficient to induce ICAM-1+ neutrophils. For the first time, we discovered that CIRP-induced ICAM-1+ neutrophils produced much higher levels of neutrophil extracellular traps (NETs). Based on these novel findings, we hypothesize that CIRP induces NET-forming ICAM-1+ neutrophils to cause ALI in sepsis. We also showed that C23, a peptide derived from human CIRP, dose-dependently inhibits CIRP-induced release of TNF-? and inhibits CIRP induction of ICAM-1+ neutrophils. Thus, we further hypothesize that C23 attenuates sepsis-induced ALI by reducing CIRP- induced NET-forming neutrophils. We will first demonstrate CIRP's induction of NET-forming ICAM-1+ neutrophils and their deleterious effects, both in vitro and in vivo. Next, we will identify key signaling pathways through which CIRP induces NET-forming ICAM-1+ neutrophils. Finally, we will examine C23's ability to suppress NET-forming ICAM-1+ neutrophils, decrease sepsis and ALI severity, and increase sepsis survival. These studies will improve our understanding of how CIRP induces NET-forming neutrophils to cause inflammation and tissue injury and support the development of C23 as a new and effective treatment for patients with sepsis and ALI.